Represents the amount of civil penalties as a part in settlement of litigation.

No definition available.

Name:	itg_LossContingencyCivilPenalties
Namespace Prefix:	itg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of disgorgement payment as a part in settlement of litigation.

+ References

No definition available.

+ Details

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Namespace Prefix:	itg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Aggregate carrying amount of the estimated litigation liability for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.25)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Interest expense (income) directly attributable to an award in settlement of litigation.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of cash paid for the settlement of litigation or for other legal issues during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3536-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_LitigationCaseAxis=itg_SettlementAgreementWithSECInvolvingPrereleasedAmericanDepositaryReceiptsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Contingencies - Legal Matters (Details) $ in Thousands	Jan. 12, 2017 USD ($)	Aug. 12, 2015 USD ($) item	Dec. 31, 2016 USD ($)
Contingencies – Legal Matters
Accrued settlement costs			$ 24,450
Settlement with S E C for Investigation into Proprietary Trading Pilot
Contingencies – Legal Matters
Number of putative class action lawsuits \| item		2
Settlement Agreement With SEC Involving Prereleased ADRs
Contingencies – Legal Matters
Payment of settlement amount	$ 24,500
Civil penalty	7,500
Disgorgement payment	15,100
Prejudgment interest	$ 1,900
Accrued settlement costs			$ 24,500
Settlement with S E C for Investigation into Proprietary Trading Pilot
Contingencies – Legal Matters
Payment of settlement amount		$ 20,300
Civil penalty		18,000
Disgorgement payment		2,100
Prejudgment interest		$ 250